Update posted with bugfixes.
For doors, there’s a system already called “Props” which is meant for this sort of thing: in Build mode (or while holding a copied slab) use Ctrl+P to convert it to a “Prop”, which is a grouped set of blocks that can grabbed and moved around like a token, but still blocks/respond to light and line-of-sight. Optionally you can Ctrl+Click on it and use the “animation” system to give it two positions it can smoothly move between- I’ve tested this to make simple elevators and moving platforms too. I don’t think I added a “hide” system like standees have but that’s a good idea.
For traps and decorations, in cases where props don’t work you could use tokens- there’s a newer “top down” setting that lets you make tokens that lay flat which may be useful for things like traps and markers. Just make sure you set the Team and vision settings appropriate for your gameplay needs.
For standee size, I’ve been thinking about how to make it work, the issue is there needs to be a “Center” block because that’s where the standee really “is”, where it sees from, etc. A better system to decide where the camera should be is something I’ve been thinking about too - especially since different players might only be able to see different small subsets of the map, or might be spoiled by knowing where things are relative to 0,0.